The present invention relates to apparatus for tamping or packing the bed of railway tracks of the type comprising a mobile chassis or frame having wheels for rolling on the track rails, at least one support for packing, or tamping, tools vertically displaceable with respect to the frame, at least two packing tools oppositely mounted on the said tool support and each constituted by an arm having at least one pick extending therefrom and provided with an end plate or blade, at least one rotary eccentric or crank-shaft to be driven by a motor journalled in a bearing rigidly connected to the tool support and comprising eccentric bearings on each of which the arm of a packing tool is pivoted by its end remote from the pick so as to impart vibratory oscillations to the said tool, and extensible connection means connecting said arm with the tool support and adapted to effect pivoting of the arm about its pivot.
Similar packing apparatus are known in which the two packing tools, which are substantially rectilinear in configuration and disposed vertically, are pivoted about a rotary crank-shaft to draw one and the other together in the ballast with their pick blades on both sides of a sleeper, or tie, by means of jacks disposed in a generally horizontal position and pivoted at their ends on the one hand to the tool support and on the other hand to the tools at a point on their arms situated generally at the mid-point between their pivot on the crank-shaft and the blade of their pick.
Such packing apparatus are robust and economic by their simplicity of construction but the vibratory oscillations transmitted to the pick stops of the tools similarly pivotally mounted on their pivot points with a horizontal jack connected to the tool support, have a somewhat circular trajectory, the radius of which is proportional to the eccentricity of the off-center bearings of the rotatable shaft.
This circular trajectory of the vibratory oscillations of the pick blades is not desirable, it having been found that the best ballast compacting results are obtained with vibratory oscillations having generally horizontal trajectories or having at the most a very flattened curvilinear form the major axis of which is tangential to the pivotal trajectory of the blade about the crank-shaft on which the tool which carries it is pivoted.
This is why this kind of direct connection of the packing tools with rotary crank shaft turning in a bearing rigidly connected to the tool support has been generally replaced, despite its advantages of simplicity, of robustness and of economy, by more complex packing devices.
There is cited by way of example and without dwelling thereon, as such are not the type to which this invention relates, but rather for interest to explain the ballast compacting effect obtained by the horizontal vibratory oscillations of the packing blades, in the best known packing apparatus the desired effect is obtained in practice, in a relatively complex manner by vertical immobilization of the pivot point of the tools and the inter-position of a connecting rod between the crank-shaft and the upper ends of the tools.
Similarly there are mentioned packing apparatus which have been proposed to obtain this same desired horizontal displacement effect without the inter-position of connecting rods between the tools and the crank-shaft but such have never passed the prototype stage due to their complexity.
Likewise there have been proposed packing apparatus in which each tool and rotatable crank-shaft which transmits vibratory oscillations thereto together form a mechanical unit pivoting around a pivotal axis situated between its two ends and integral with the tool support; the upper end of the said tool being connected to the tool support by a jack adapted to provoke its pivoting around the said axis. In these packing apparatus each tool comprises a gear box pivotable on the pivotal axis integral with the tool support and comprising an upward extension provided for its connection with the jack and in which is housed the crank-shaft, similarly, a fork has a vertically sliding bearing housed between the prongs of the fork and pivoted on the off-center part of the crank-shaft; this fork being angularly connected by rigid attachment to another rotary shaft carried by the said gear box which is rigidly connected, on the outside, the lower part of the packing tool. This construction in which only the horizontal vibratory oscillations are transmitted by the rotatable crank-shaft to the fork integral with the lower part of the tool carrying the packing blade is, it goes without saying, relatively complex and fragile due to the fact of the numerous parts functionally integral one with the other constituting each packing tool.
It has also been proposed, but to another end, to actuate the jack to provoke the pivoting of the packing tools to the point where the member which establishes the connection between the said tools and the crank-shaft is pivoted to the said tools or operates on these. In such packing apparatus the crank-shaft no longer turns in a bearing rigidly fixed on the tool support but is rather suspended on the rod of a jack adapted to pivot the tools and connected to the said tool support either by pivoting or by rigid attachments. In the first case the tools are elbowed and themselves suspended by their elbows from the tool support by the intermediary of a resilient connection in the horizontal direction. In the second case the tools are similarly elbowed but each conforms in two telescopic parts one of which is connected to the crank-shaft and the other is pivoted by its elbow to a pivot integral with the tool support. These two proposals result in a movement, not explicitly sought wherein the stops of the packing tools effect generally horizontal vibratory oscillations. The suspension of the vibrator comprises a bearing and a crank-shaft and its motor at the end of the rod of the jack is delicate and fragile, and the necessity of permitting the free pivotal play of the tools in making these extensible by a telescopic system or, alternatively, in connecting them to the tool support by elastic suspensions is complex, is not rational and again increases the fragility of this system of connection between the packing tools and the tool support.
Examples of patents illustrating prior developments are: Japanese Pat. No. 35-12706 of May 1958; U.S. Pat. Nos. 3,016,023 of Jan. 9, 1962; 3,669,025 of June 13, 1972; 3,998,165 of Dec. 21, 1976; Austrian Pat. No. 206,915 of May 28, 1958.
It is an object of the present invention to provide with simple packing apparatus of the type cited at the beginning of this specification in which the packing tools are directly connected to a rotary eccentric or crank-shaft turning in a bearing rigidly fixed to a tool support, substantially horizontal vibratory oscillations.